Certain standards provide specifications for cellular telecommunications network technologies, including radio access, the core transport network, and service capabilities. For example, Release 12 of the 3rd Generation Partnership Project (3GPP) provides enhanced support of Heterogeneous Networks for co-channel, dedicated frequency, and multicarrier. One objective is to avoid co-channel interference, for example by specifying solutions to mitigate uplink and downlink imbalance. In view of this, one aspect of the enhanced support is to allow an uplink enhanced dedicated channel (E-DCH) to be decoupled for Rel-12 terminals. E-DCH decoupling in this context is the decoupling of the serving E-DCH cell and the serving high speed downlink shared channel (HS-DSCH) cell from each other. Doing so can improve the performance in the presence of imbalance between the uplink and the downlink, characteristic to the heterogeneous network environment.
In the Radio Link resources handling, the E-DCH and the HS-DSCH may be setup, added, and/or reconfigured separately, using Radio Link Setup, Radio Link Addition and/or Radio Link Reconfiguration procedures and associated radio link messages.
In the current Node B Application Part (NABP) and the Radio Network Subsystem Application Part (RNSAP) specifications, the establishment of an E-DCH on one or more radio links are supported. The Serving E-DCH Radio Link Information Element, “Serving E-DCH RL IE” may be used for example to indicate the Serving E-DCH RL.
However, the existing 3GPP standard (i.e. pre-Release 12 of the 3GPP standard) specifies that, if the serving E-DCH and the serving HS-DSCH are not in the same cell, the node B or the drifting network radio controller (DRNC) should reject the radio link resource handling procedures, and as such do not support a decoupling procedure.
For example, the legacy procedures couple the serving E-DCH and HS-DSCH, as shown from the extract below from 3GPP Technical Specification TS 25.433 (pre Release 12), for example the Abnormal Conditions according to section 8.2.17.4 which relate to a Radio Link Setup Request procedure, and which states:
If the RADIO LINK SETUP REQUEST message contains the HS-PDSCH RL ID IE and the Serving E-DCH RL IE but the Serving HS-DSCH Radio Link and the Serving E-DCH Radio Link are not configured to be in the same cell then the Node B shall reject the procedure using the RADIO LINK SETUP FAILURE message.
Thus, from above it can be seen that the current (Pre Release 12) 3GPP specifications relating to NABP or RNSAP do not permit decoupling, which results in a backwards compatibility problem between a radio network controller (RNC) configured for Release 12 or later, and pre-Release 12 Node Bs and DRNCs.